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Radar Sea Return-JOSS I
NAVAL RESEARCH LAB WASHINGTON DC
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The 4FR System was employed to obtain calibrated sea return data for various sea states as a function of radar wavelength, polarization, and depression angle. Surface truth was acquired simultaneously, utilizing laser altimetry, aerial photography, and observers stationed on Argus Island. Processing of the radar backscatter data is complete, and the median value of the normalized radar cross section NRCS sigma sub 0 of the sea has been determined as a function of radar and surface parameters. These data have been incorporated with the data resulting from previous measurement programs to form a comprehensive data bank of the parametric behavior of the median value of sigma sub 0, from which the following conclusions may be drawn 1 The NRCS of the sea approaches a limiting value with increasing roughness for all frequencies and polarizations. 2 For depression angles 5 degrees to 60 degrees, the growth of the NRCS may be approximated by simple empirical formulas. 3 For the rougher conditions observed in the JOSS I mission, the NRCS data implied the presence of the equilibrium range spectrum. 4 The spectrum exhibited a characteristic dip at the higher wave numbers for calm sea conditions. 5 The cross-polarized return approaches a limiting value with increasing wind.
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